Method for flotation concentration in coarse size range



April 5,1960 E. A. SCHOELD ETAL 2,931,502

METHOD FOR FLOTATION CONCENTRATION IN COARSE SIZE RANGE Filed July 2, 1956 5 Sheets-Sheet 1 INVENTORS Edmund A. Schpeld Jack D. Nabors Joseph S. Reiter W ZZMMA ATTORNEYS E A. SCHOELD ETAL 2,931,502

METHOD FOR FLOTATION CONCENTRATION IN COARSE SIZE RANGE Filed July 2. 1956 April 5, 1960 5 Sheets-Sheet 2 INVENTORS Mar m ai D S A h d C 0. na% uJ m J 0 E ATTORNEYS April 1960 E. A. SCHOELD ETAL 2,931,502

METHOD FOR FLOTATION CONCENTRATION IN COARSE SIZE RANGE Filed July 2, 1956 5 Sheets-Sheet 3 6RE-- [scRuBBER Fc| Ass|F|ER CONDITIONER 45 47 k I; k k

FLOTATION 45 CELLS DRYING AND PRODUCT STORAGE FLOOR A FLOOR 8 x l f I 54 FLOTAT ON CELLS H MIDDLINGS 52 TO GRINDING TAILINGS K TO WASTE INVENTORS. 1 l g 5 Edmund A. Schoeld Jack D. Nabors Joseph S. Reiter mfiwg W ATTORNEYS United States Patent METHOD FOR FLOTATIQN CONCENTRATIONIN COARSE SIZE RANGE Edmund A. Schoeld, Jack D. Nabors, and Joseph S.

Reiter, Carlsbad, N. Mex., assignors to Potash Company of America, Carlsbad, N. Men, a corporation of Colorado Application July 2, 1956, Serial No. 595,500

21, Claims. (Cl. 209-164) This invention relates to the art of concentrating minerals by a flotation procedure and more particularly relates to the concentration of a coarse sylvite fraction of sylvinite ore by a novel type of flotation separation.

Industrial demand is requiring potash refiners to produce larger tonnages of high-grade sylvite as a coarse product, a minus 6 to a plus 28 size range being representative, and a 60 percent grade in K 0 equivalent is now standard for such product. Consequently, many ice of material can be treated in a relatively small space and in a relatively short treatment time. 1

Other objects reside in novel details of construction and novel combinations and arrangements of parts, all of which will be described in the course of the following description.

procedures which would provide a satisfactory product in a standard flotation size range are inadequate for this purpose, since they will not meet grade requirements in treating the coarse material. As an example, flotation of sylvite using an aliphatic'amine with a blinding agent such as starch or guar flour has been adopted commercially in several plants with good results. However, this procedure when applied to a sized minus 6 plus 28 mesh ore in standard flotation equipment will not make the metallurgical separation.

This application is a continuation-in-part of our copending application Serial No. 526,720, filed August 5,

1955 (now abandoned), wherein We have described an,

effective treatment for obtaining coarse sylvite concentrate and have shown and described apparatus well suited for performing the novel type of flotation separation, and features described but not claimed herein have been claimed in said application.

In our earlier application, we noted the froth-free surface of the separation stage as being one of the distinctive, features of the invention. Mineral, such as sylvite, when properly coated or filmed in the conditioning stage before flotation, attaches to air bubbles and becomes quite buoyant in the brine of the treatment and then will float on the surface without requiring a froth carrier, although aeration is a highly effective means of causing submerged particles to carry to the surface.

We have observed the flotation action in a transparent cell and noted the rapid rise of very coarse particles, to

the surface as soon as air bubble attachment occurs. In addition, we have found that a very eflective concentration can be attained by a two-stage flotation treatment using an amount of reagent less than required to float all the sylvite at the first stage, and adding additional reagent before the second stage so as to float substantially all of the sylvite, most of which remains. in the form of middlings particles.

Accordingly, it is an object of this invention to provide a simple, efiicient and economical process for the recovery of a high-grade sylvite in a coarse size range.

Another object of the invention is to provide a simple, efficient and economical milling circuit for the production of a high-grade coarse sylvite concentrate and a high-grade standard size sylvite product.

A further object of the invention is to provide simple, durable and eflicient apparatus for performing a novel type of flotation separation on various materials.

Still another object of this invention is to provide a type of flotation cellin which a relatively large, volume The practice of the invention will be best understood by reference tothe, accompanying drawings, and in the drawings in the several views of which like parts bear corresponding reference numerals:

Fig. l is a front elevation of a typical cell for practicing the novel flotation treatment, a portion being broken away to show interior arrangements;

Fig. 2 is an end elevation of the cell shown in Fig. 1 and showing the arrangement of the tailings discharge control;

Fig. 3, is a fragmentary vertical section through the cell shown in. Fig. 1, drawn to an enlarged scale, and representing the circulation and flotation action-of a typical operation;

Fig. 4 is a section taken along the line 4-4, Fig. 3;

Fig. 5 is a flow sheet representation of a typical twostage circuit for the practice of this invention;

Fig. 6 is another flow sheet representation of a typical circuit combining a circuit such as shown in Fig. 5 with a typical halite flotation circuit for the treatment of sylvinite ore; and

Fig. 7 is another flow sheet of a combined circuit in which the, final treatment involves a typical circuit for flotation of sylvite with an amine collector. I

Where reference is made in the specification to a coarse ore or coarse product, we intend to designate a material having a major portion of its content in sizes substantially larger than minus 28 mesh or standard flotation size. Standard Tyler mesh sizes are designated throughout the specification, anda minus 6 plus 28 mesh product may be considered a typical coarse commercial product by present standards, but it is recognized that even coarser products may become standard at some later date and the present invention isnot limited to producing products withinsuch a range. I Brine as used herein is intended to designate all the various brines of potash ores which may be formed in a wet treatment of such materials. In a treatment of sylvinite ore, for example, the brine usually will be saturated with respect to the sodium chloride and potassium chloride. content, although throughout a portion of the circuit it may be saturated with respect to potassium chloride only. For purposesof the present invention it will be advisable to have the brine saturated with respect to whatever mineral is being floated at the flotation stages, although it is sometimes helpful to have it undersaturated with respect to other soluble constituents at the dewatering stages following the main separation.

High density pulps as used herein would apply to any mixtures having a solids content of one part to two parts brine, or greater, and usually will be on the order of 1:1. The term ore as used herein is intended to designate dry material or material which although wetted does not have enough associated liquid or brine to maintain the particles in a state of substantial suspension. Pulp refers to a mixture of, ore and brine having sufficicnt liquid content to act as a carriervehicle for substantially all of the solids of the ore.

High velocity as applied to the gas or brine discharge is intended to designate a rate of flow substantially in excess of that required to obtain aeration or circulation in conventional flotation practice. Filming" or fcoating of particles as referred to herein is intended shown in our co-pending application, Serial No. 526,720

(now abandoned) for example, but we have shown in Figs. 1 to 4, inclusive, a preferred form of cell for performing the separation.

This unit comprises an elongated tank 12, having a sloping bottom 13, upright front and rear walls 14 and 15 respectively, which preferably incline outwardly away from bottom 13 and have overflow lips 16 at the top. An end wall 17 at the feed end and another end wall 18 at the tailings discharge end complete the tank enclosure.

A feed box or chute 19 is provided to deliver ore through a large slotted opening 20 in the upper portion of wall 17 as the feed to the cell.

An opening 22 admits the non-floated material or tailings into a depending sump member 23 the outlet 24 of which is regulated by an automatic valve 25, the functioning and details of which will be described later. A series of submerged partitions or baflles 26 located at intervals along the bottom of the tank define a series of treatment stages and regulate the flow of non-floated material along the tank bottom. Preferably each partition has an opening 27 to simplify washing the cell during shut downs.

A header 28 connected with a suitable source of supply (not shown) delivers brine to a series of downwardly directed nozzles 29, the lower ends of which terminate near but spaced from bottom 13 and substantially centrally of the enclosed area defined by adjacent partitions 26. As shown in Fig. 3 each nozzle comprises a pipe or tubular portion 30 into which a gas supply conduit 31 enters intermediate its ends as indicated at 32. The bore of tube 30 is reduced adjacent the entrance 32, as by the tube 33 of reduced diameter, and provides an aspiration effect to substantially aerate the brine during its passage to the discharge end of nozzle 29 in a high velocity movement.

By reason of the valve control of tailings discharge through outlet 24, the sump 23 functions as a pulp thickener to create a super-elevation pressure in the fluidized pulp. In the automatic control illustrated in Figs. 1 and 2, a differential pressure controller 35 has an openended tube 34 extending down into the sump 23 and a second open-ended tube 36 extends below the brine level but near the surface so as to transmit to controller 35 measurements of varying pressure due to changing brine level or density. The setting of valve is regulated automatically in accordance with the pressure variations and thus maintains a substantially uniform density condition in cell 12.

In operation, ore or pulp may be introduced into tank 12 through feed box 19 and opening 20, while brine and an aerating gas are introduced through nozzles 2%. Tailings discharge through outlet 24 is controlled by valve 25 to establish sufficient super-elevation pressure 5 of the pulp to create a high density in the discharge. Unlike the usual flotation treatment, this operation utilizes a high-density pulp with a major portion of the solids content not rising appreciably above the level of the top surfaces of partitions 26, except as the solids are washed over the partitions in their progressive flow through the cell.

The reagentized ore feed is in proper condition for flotation and the high velocity discharge of aerated brine sweeps in and about the submerged body of particles to maintain them in a loose, tumbling condition providing a large amount of air-solids contact. Due to the coarse size of the particles under treatment, a single air bubble attachment may be inadequateto provide an elevating 4 action but we have observed that where several bubbles attach to a particle it rises rapidly to the surface and floats readily without air bubble attachment when exposed to atmospheric air. In fact we have observed many particles comingfalmost entirely out of the brine and floating with only a minor portion of their mass submerged.

Due to the volume of brine used and overflowing, surface flow is essentially transverse to the progressive flow through the cell, and on reaching the surface the particles are carried rapidly by this flow to one of the lips 16 where they overflow to discharge. flotation is so rapid due to the high degree of air-solids contact that the floating particles sometimes cause a jamming at the weirs with some particles being submerged and falling back into the cell. Rising air bubbles frequently attach to such particles and whenever suflicient air is thus encountered they are re-elevated to the surface and thus ultimately discharge as concentrate.

The retention or delaying action of partitions 26 provides substantial recirculation at each treatment stage and floatable mineral not discharged as concentrate in the first stage is subjected to repetitions of the treatment just described in its progress through the cell. As a consequence, about the only floatable mineral passing through opening 22 into the sump thickener stage is true middlings particles which are purposely kept out of the concentrate to insure high grade of product. The features of this control will be described subsequently.

The fact that the main solids charge of the feed remains substantially submerged except as elevated by air bubble attachment permits a much higher volume of feed to be circulated than would be possible with any other type of flotation separation. The submerged particles are not suspended in the usual sense, in that no appreciable quantity of the non-fioated material is swept into the upper portion of the pulp body by the aerated brine agitation, although the submerged body is suspended sufliciently so that the circulating brine flows readily between the particles and carries entrained air into all areas adjacent the cell bottom. Floatable particles begin their rise at all elevations within the pulp body, whenever adequate air adherence is attained, and the rate of rise is independent of the rate of ascending brine flow.

The velocity of discharge of aerated brine may be varied in accordance with the volume of ore under treatment and the overflow requirements of the operation. When large volume, high velocity discharge is attained, the sweep of the brine may cause a slight vortex condition at the surface, whereas under reduced input the surface will be relatively quiescent except for the activity of the bubbles rising to and breaking up on the surface. In any event, there are distinct up and down currents at all times during operation with the discharging brine spraying out along the bottom, then rising, and a portion of same swinging back toward the nozzle and moving downwardly.

A major portion of the brine rises, and on reaching the surface flows directly to and over the lips 16, and it is this flow that sweeps the floating concentrate to discharge. Figs. 3 and 4 show a representation of this action with the arrows indicating the general flow pattern. The surface flow divides substantially along the center .line of the cell and flows in substantially equal volume to the overflow lips of the front and rear walls 14 and 15. In addition to the up and down brine flow at each stage, there is also a pronounced flow lengthwise of the machine towards the tailings discharge.

The provision of the bafiies 26 and the regulation of dis- 7 In this action, the

turbed by the agitation and the measurements of. controller 35 are a true indication. of the pressure difierentials.

Again referring to Figs. 3 and 4, the distribution of solids, gas and floating particles is representative of observed conditions and while more schematic than actual scale depicts the relation of. particle size to air bubbles, and the distribution of floating and non-floating material in the cell, as well as the circulatory flows previously described. Dash line arrows indicate particles actually floating, except on the surface, whereas a single bubble attachment represents a particle which is merely suspended or sinking. I

With this understanding of the novel flotation action, certain typical flow sheets will be described to explain preferred procedures in the practice of this invention. Fig. 5 depicts a two-stage concentration employing gravity flow, with initial concentration on floor A and the final concentration stage at a lower level on floor B. A sized ore, preferably in the minus 6 plus 28 range, is fed into a scrubber ll), preferably of the rotary drum type, with sufficient brine added to thoroughly separate adhering clay slimes in the progress of the material through the scrubber.

The ore discharge of the scrubber is delivered into a classifier, preferably a spiral-type classifier 41, which functions as a dewaterer, with the raked product being discharged into a conditioner 42. Excess brine passes across an overflow and returns to the brine system. If desired part of the conditioning may be done in the classifier raking zone, in which case the time of retention is limited to provide adequate conditioning time in the two stages. The conditioner discharges reagentized ore to one or a plurality of flotation cells, such as the cells 44 which are duplicates of cell 12 of Fig. l.

The concentrate of this operation comprising clean, coarse sylvite passes into a line 45 and thence to another classifier 46, which also acts as a dewat-ering device. The overflow 47 from this operation goes to the brine return system while the raked product is dried and then goes to storage or market. The tailings or underflow of the flotation separation passes into a line 48 which conducts it to floor B as the feed of that operation.

The line 48 discharges into a classifier 49, and preferably some of the collector reagent is introduced into the raked product of this stage. Excess brine overflowing at 59 goes into the brine return system. The raked product discharge goes into a conditioner 51 where more reagent may be added. The conditioning should provide a' sufiicient quantity of reagent to insure flotation of all sylvite whether in the form of middlings or separate particles, and this reagentized ore becomes the feed of the next flotation stage 52, generally designated middlings flotation.

If desired, the feed to the flotation cells 44 or 52 may be a pulp, but preferably is wetted ore that is not suspended in a carrier brine. Under such circumstances less attrition and securing of coated surfaces results with increased flotation when the ore is pulped by the rims introduction at the flotation stage. This is another reason why we prefer to feed a heavy charge of ore to the flotation cells, as a rapid flotation occurs when the particles encountered the aerated brine, and a high percentage recovery is attained.

The float concentrate of the cells 52 passes to a classiliter 5% through a line $3 with the overflow 55 of the classifier being discharged into the brine return system,

while the raked product comprising mostly middlings discharges to grinding prior to treatment by well-known methods for recovery of the sylvite in reduced sizes. The tailings from cells 52am delivered to another classifier 57 by a line 56, subjected to a dewatering treatment with the separated brine passing into the brine return system, while the raked product is a waste product i and is passed to waste.

' corresponding to that shown in Fig. 5.

cflicient concentration of coarse sylvite is attained, in that only enough reagent is provided for the conditioning ahead of flotation to float the true sylvite fraction without contamination from middlings. The second conditioning of the first flotation reject is calculated to float substantially all the middlings, and the sylvite content of this fraction may be released by grinding, and then recovered by various methods. In a typical test operation performed according to the Fig. 5 flow sheet, the concentrate analyzed 94.7 grade, and the tailings contained only 1.6% KCl. 1

In our .co-pending application, Serial No. 526,720 (now abandoned), we have shown apparatus in Figs. 5 through 11 .which is generally similar to apparatus illustrated inFigs. .1 through 4 of this application and is capable of performing the novel flotation separation of the present invention. However, the earlier form did not provide distinct flotation stages and the rate of flow along the. bottom was not restrained except by the impedance of the tailings discharge. The high. velocity discharge of aerated brine directed toward the sloping bottom accelerates the movement of the non-floated solids, and in some instances at least, results in the entrainment of a substantial amount of mineral that is ready to float but is buried beneath other solids which prevent the necessary air contact for floating it. j

Consequently, the baffles 26 of the present application insure sufi'icient retention time at each aeration stage to provide adequate air-solids contact for, all mineral ready to float and by having repetitions of the delayed move ment, mineral not floating at one stage is exposed at sub-- sequent stages due to the tumbling movement provided and eventually receives the required air attachment to elevate it to the surface.

Similarly, the density control of the tailings discharge in conjunction with the partition or baflie arrangement adapts the flotation unit to treat a greater tonnage of ore on a more efiicient basis. Comparative test operations before and after incorporating the partitions or baflles and the density control established that tonnage treated could almost be doubled with improved concentration and reduction in tailings losses. The change also resulted in the brine requirement being held at a minimum due to reduction in brine discharge with the tailings by reason of the increased density at the tailings discharge.

Fig. 6 is a circuit arranged to utilize a standard halite flotation plant circuit as the final sylvite recovery, after a. coarse concentrate has been produced by an operation Such a standard circuit has been shown in Weinig, Patent No. 2,211,397, which is generally'representative of the refinery circuit of the Potash Company of America plant at Carlsbad, New Mexico. In Fig. 6 and in Fig. 7, various treatment stages have been designated by equipment names to avoid a multiplicity of numbering.

In the operation shown in Fig. 6, ore from the crushing plant designated Fine Ore is stored in bios supplying the operation, and after drying is conducted from the bins at a measured rate to a sizing device designated screcns or hydraulic classifiers which reject plus 6 sizes. The screened product discharge of the screen comprises the feed to another screen, preferably a shaking screen, which discharges minus 28 mesh sizes as a prodnot for the standard circuit. The remaining ore is in the minus 6 plus 28 mesh range and is fed to a scrubber in the granular circuit where brine (A) is introduced and the slimes associated with the ore are separated.

The scrubber discharge passes to a classifier with the overflow going to the (A) brine return circuit. The brines of the coarse concentration circuit and the standard circuit must not be mixed as the leaded brine essential to the halite flotation impedes the efhciency of the amine flotation. The raking stage of the aforesaid classifier may include reagent introduction and the raked product discharge passes into a conditioner with addi- 7 tional reagent added and suflicient conditioning time allowed so that the discharge of the conditioner is in proper condition for the flotation treatment of the granular circuit.

The flotation action of the granular circuit is similar to that previously described with reference to the cell shown in Figs. 1 and 2, and a clean, coarse sylvite concentrate is collected at this stage. This concentrate passes to another classifier from which it discharges in a substantially dewatered condition and thence to a dryer as a final product of the treatment designated granular product." The tailings of the flotation separation are delivered to another classifier for dewatering and thence to a conditioner with reagent introduction in an amount adequate to float all middlings. Brine from each of these classifiers is delivered into the (A) brine return system designated Brine A Return."

The conditioned ore of the second conditioning step constitutes the feed to a middlings flotation stage in which the aerated brine is utilized to cause flotation of the middlings content together with whatever sylvite passed with the tailings from the first flotation stage. The tailings of this treatment are passed to a classifier for dewatering and thence to the salt dump designated Granular Tailings Discard. The brine of this separation discharges into the (A) brine return system designated Brine A Return. The flotation concentrate which is primarily middlings discharges into a classifier which dewaters it with the middlings going to a rod mill, which also may receive the plus 6 reject of the fine ore screen as indicated by the optional flow, and (B) brine from the (B) brine return system, designated Brine B System also is introduced into the rod mill.

The ground product of the rod mill is fed to a crubber together with the minus 28 product of the second screen separation and is pulped with (B) brine to make a suitable flotation feed for the standard circuit. The scrubber discharge receives additional (B) brine return to prepare the pulp for halite flotation. Schoeld, Patent No. 2,703,646, describes various reagent combinations well suited for this purpose. After proper conditioning the pulp is fed into standard flotation cells, preferably operated as a rougher-cleaner circuit, and the haiite together with any slime impurities of the pulp are collected in a froth and removed as a tailings product designated standard tailings discard, while the nonfloated material comprising clean sylvite is discharged as the underflow concentrate, and is thickened or dewatered, filtered and dried as another final product of the treatment, designated standard product."

The halite product separated at flotation in the standard circuit passes to a thickener and then to a filter with the filtrate discharging into Brine B, while the washed cake goes to the salt dump designated standard tailings discard. The overflow of the respective thickeners constitutes the main supply to the (B) brine surge tank (not shown) from which it is delivered by a pump to the designated points of (B) brine input into the operation.

The circuit shown in Fig. 7 differs from that just described in several respects and particularly in that only one brine system is required and brine from the surge tank can be delivered to any input point in the circuit. Otherwise the operation is substantially the same as described for Fig. 6 with the exception that the position of concentrate and tailings in the standard circuit is reversed and the conditioning for flotation following classification utilizes amine reagents for sylvite flotation. At the flotaion stages in each circuit sylvite is collected as the floated concentrate, which is then filtered and dried for discharge as a finished product. The flotation tailings (NaCl) go to a salt filter with the cake being discharged to the dump, while the filtrate goes to the brine return thickener and thence to the surge tank. The sludge discharge of this thickener also passes to the dump as a tailings discharge.

As shown in Fig. 7, thefine ore, afterdrying, passes 8 through a segregating screening stage designated screens and/or hydraulic classifiers which produce +6, -6+28, and -28 fractions. The --6+28 fraction is conducted to the granular circuit where it is passed through a scrubber, classifier and conditioner so as to be in proper condition for a flotation separation. The KCI froth concentrate of this separation is discharged into a classifier with the raked product passing to a dryer and then dis charged as granular product.

The NaCl underflow product or tailings of the flotation separation, which contains most of the middlings, passes into a classifier, the raked product of which is conditioned and introduced into a middlings flotation stage, the underflow product of which is classified and the raked product of that separation which contains almost no KCI is discharged as Granular Tailings Discard. The froth concentrate containing the middlings is conducted to a classifier, the raked product of which goes to a rod mill of the standard circuit, while the overflows of said classifiers are returned to the brine system of the circuit.

The rod mill discharge and the -28 mesh product of screening are combined as the feed to a classifier in the standard circuit, the overflow is conducted to a hydroseparator for slimes elimination, and the hydroseparator underflow combines with the classifier'raked product as feed of the standard flotation circuit, which is first conditioned and then introduced into the flotation stage, preferably comprising a rougher-cleaner separation as indicated by the double designation of flotation cell. The rougher underflow is filtered and discharged as standard tailings discard," while the rougher froth comprises the feed to the cleaner cell or cells. The cleaner froth, which is a satisfactory grade KCl product, is filtered, dried and discharged as standard product.

In order to provide a more readable flowsheet, both Figs. 6 and 7 omit some details of brine circuiting. However, the description makes frequent reference to the brine return system, and a circuit as aforesaid will direct brine when separated from solids to a surge tank" or other storage facility for reuse in the circuit according to prevailing commercial practice. Usually, such brine is first directed into a thickener to provide a clear brine return to the surge tank, while the thickener sludge may be treated in the circuit in one of the various ways now practiced commercially in this art. In this Way much valuable KCl in solution is retained in the plant for ultimate recovery.

In either of the granular circuits shown in Figs. 6 and 7, it will. be advantageous to limit the initial conditioning to use of less reagent than required to float all the sylvite. By so doing few middlings will carry into the first concentrate, thus assuring satisfactory grade of the coarse product. If some sylvite passes from this stage with the tailings it does not represent a loss, as it will float readily at the next stage under the supplementing effect of the added reagent and thus will reach the rod mill with the middlings. The grinding may expose new surfaces, but conditioning is provided after grinding so that .the feed to the standard circuit is in proper condition for flotation. By proper control of the entire circuit, final tailings losses can be held to 1% or slightly higher.

In this connection, the choice of eflicient reagents will have a beneficial effect on the operation. In our copending application, Serial No. 526,720 (now abandoned), we have described the use of reagents well suited for the requirements of coarse flotation. may be used in the standard amine circuit as well, or, if preferred, any of thestandard aliphatic amines such as Armour and Co. Armac TD or HTD may be used.

In the form of cell shown in Figs. 1 and 2, we have provided a single nozzle for the discharge of aerated brine at each treatment stage, but for some treatments it will be preferable to have a plurality of nozzles to effect a more widespread distribution of the aerating gas at each such stage. For example, in a pilot plant test with Such reagents a cell substantially as shown in Figs. 1' and 2, we provided two nozzles to each stage between the end wall atv the feed end and the firstbaflie, and between each set of successive baffles. a line approximating the lengthwise center line of the cell.

This cell was six feet long, eighteen inches wide at the top, three inches wide at the bottom, eighteen inches deep at the feed end and twenty-four inches deep at the discharge end. Seven balfies were positioned lengthwise of the cell, each being six inches in height, and'a total of 14 nozzles were provided, arranged as described above. The pilot plant circuit was essentially the same as shown in Fig. 5 with one cell, as aforesaid, at the coarse concentrate stage and a similar cell at the middlings flotation stage.

Operation of this plant on the date of test gave composite analyses of:

Percent KCl Ore .feed (sylvinite) 41.6 Granular concentrate (6+28 mesh) 97.0 Granular middlings 10.7 Granular tailings 1.6

The rate of ore feed to the coarse concentrate cell was approximately 100 tons per day. From the foregoing it will be apparent that the process of the present invention, in addition to satisfying grade requirements provides a high capacity treatment in small volume equipment requiring little operator control.

In our co-pending application, Serial No. 526,720 (now abandoned), we have noted the benefit to grade of product resulting from reduction in" amount of collector reagent utilized in the conditioning ahead of the first flotation stage. However, that disclosure does not set forth the relationship of reagent quantity to sylvite flotation capacity. As previously stated herein, we now seek to control reagent quantity in the first flotation to provide less than the amount of collector requiredto float the, entire sylvite content so as to provide a close control of concentration. Under such conditions true sylvite will float more readily than middlings, and as a result only a very small amount of middlings is collected in the first concentrate. I

Thereafter, we add suflicient collector at the second conditioning stage to be capable of floating the entire remaining sylvite content so as to provide a close control on tailings losses and consequently even middlings particles which are mostly halite combined with a lesser amount or sylvite will float sufficiently so that, as shown in the test report, the final tailings contain substantially less than two percent sylvite. While various collector reagents may be used in this treatment, we prefer to use a reagent combination of amine collector and a modifier for sylvite of the type disclosed in our aforesaid application.

The present invention represents a departure from conventional flotation treatments in that crushed ore before beneficiation is subjected to a size separationfor rejection of extreme fines and extreme coarse fractions. This may be accomplished by a screen separation, as in our preferred practice, or hydraulic classification may be used when desired; Thereafter, the sized ore is scrubbed, conditioned and fed to flotation, preferably without pulping,

' bulk of the sylvite is floated and removed as concentrate in the first flotation treatment, and consequently the mid dlings concentrate, which together with the +6 reject is the product requiring grinding, represents only a small These nozzles were positioned along 10 of the halite before grinding represents a highly important savings in the total processing cost.

We claim: 1. The process of concentrating sylvinite ore in a coarse size range, which comprises the treatment ofzone, subjecting the ore in said flow to the action of a fraction of the total weight of ore taken for treatment.

The prior beneficiation in no way impairs the efliciency ofthe final standard flotation and the savings in milling succession of downwardly sweeping streams of brine and air in the lower portion of said zone so as to repeatedly tumble and loosen the particles in said progressive flow and provide a high degree of air-solids contact, causing filmed sylvite particles to rise to the surface by air bubble attachment at varying depths throughout the flowing body of solids, and moving particles rising to the surface to points of overflow in a direct surface flow.

2. The process of concentrating sylvinite ore in a coarse size range, which comprises the treatment of crushed sylvinite ore from which slimes and fine sizes have been removed, conditioning such ore with a collector reagent for sylvite, feeding the ore into a confined treatment zone, inducing a progressive flow of a high density portion of the solids of the feed along the lower portion of said zone to a point of tailings discharge from said zone distant from the point of feed introduction, subjecting the ore in said flow to the action of a succession of downwardly sweeping streams of brine and air so as to repeatedly tumble and loosen the particles in said progressive flow and provide a high degree of air-solids contact,

causing filmed sylvite particles to rise to the surface by air bubble attachment at varying depths throughout the flowing body of solids, and moving particles rising to the surface to points of overflow in a direct surface flow.

3. The process of concentrating sylvinite ore in a coarse size range, which comprises the treatment of a pulp of crushed sylvinite ore from which slimes and fine sizes have been removed, conditioning such ore with a collector. reagent for sylvite, feeding the ore into a confined treatment zone, inducing a progressive flow of a high density portion of the solids of the feed along the lower portion of said zone to a point of tailings discharge from said zone, subjecting the ore in said flow to the action of a succession of downwardly sweeping, high velocity streams of brine and air in the lower portion of said zone so as to repeatedly tumble and loosen the particles in said progressive flow and provide a high degree of air-solids contact, causing filmed sylvite particles to rise to the surface by air bubble attachment at varying depths throughout the flowing body of solids, and moving particles rising to the surface to points of overflow in a direct surface flow;

4. The process of concentrating sylvinite ore in a coarse size range, which comprises the treatment of crushed sylvinite ore from which slimes and fine sizes have been removed, conditioning such ore with a collector reagent for sylvite, feeding the ore into a confined treatment zone of substantial length, inducing a progressive flow of a high density portion of the solids of the feed along the lower portion of said zone to a point of tailings discharge from said zone, subjecting the ore in said flow to the action of a succession of downwardly sweeping streams of brine and air in the lower portion of said zone so as to repeatedly tumble and loosen the particles in said progressive flow and provide a high'degree of'airsolids contact, causing filmed sylvite particles to rise to the surface by air bubbleattachment at varying depths throughout the flowing body of'solids, and moving particles rising to the surface to points of overflow in a direct surface flow. i

5. The process of concentrating sylvinite ore in a coarse size range, which comprises thetreatment of crushed sylvinite ore from which slimes and fine sizes have been removed, conditioning such ore with a collector reagent for sylvite, feeding the ore into a confined treatment zone, inducing a progressive flow of a high density portion of the solids of the feed along the lower portion of said zone to a point of tailings discharge from said zone, subjecting the ore in said flow to the action of a succession of downwardly sweeping streams of brine and air so as to repeatedly tumble and loosen the particles in said progressive flow and provide a high degree of airsolids contact, causing filmed sylvite particles to rise to the surface by air bubble attachment at varying depths throughout the flowing body of solids, and moving particles rising to the surface to points of overflow in a direct rapidly-moving surface flow.

6. The process of treating sylvinite ore, which comprises sizing crushed sylvinite ore to reject material in substantially the range of plus 6 and minus 28 sizes, scrubbing the said minus 6 plus 28 screened fraction for elimination of clayey slimes, conditioning the deslimed ore with collector reagent for sylvite in a quantity less than required to float the entire sylvite content of the ore, subjecting the reagentized ore to a flotation separation to obtain a high grade coarse concentrate, conditioning the non-floated material of said first flotation with additional collector reagent for sylvite in a quantity suflicient to float substantially all the sylvite content, subjecting said material to a second flotation treatment to obtain a middlings concentrate containing substantially all the remaining sylvite content of the pulp, grinding said middlings concentrate to a standard flotation size, conditioning the ground ore with a collector reagent for one ore constituent, and subjecting such conditioned ore to froth flotation to obtain a standard size sylvite concen" trate as a separated product of the flotation separation.

7. A process according to claim 6, in which the minus 28 screen reject comprises a part of the feed to the final conditioning stage.

8. The process of treating sylvinite ore, which comprises sizing crushed sylvinite ore to reject material in substantially the range of plus 6 and minus 28 sizes, scrubbing the said minus 6 plus 28 screened fraction for elimination of clayey slimes, conditioning the deslimed ore with collector reagent for sylvite in a quantity less than required to float the entire sylvite content of the ore,

subjecting the reagentized ore to a flotation separation to obtain a high grade coarse concentrate, conditioning the non-floated material of said first flotation with additional collector reagent for sylvite in a quantity suflicient to float substantially all the sylvite content, subjecting said material to a second flotation treatment to obtain a middlings concentrate, grinding said middlings concentrate to a standard flotation size, conditioning the ground ore with a collector reagent for halite, and subjecting such conditioned ore to froth flotation to obtain clean sylvite as a nonfioated, standard size concentrate.

9. The process of concentrating potash minerals .which comprises the treatment of a conditioned, high-density pulp in an elongated, confined zone of substantial vertical extent, moving a high density portion of the pulp progressively along the bottom of said zone from a point of feed introduction at one end to a point of tailings discharge at its opposite end with only a minor quantity of non-floated solids in suspension in the upper portion of said zone, subjecting said pulp flow at a series of stages between feed introduction and tailings discharge to an aerating action induced by a high-velocity discharge of an aerating composition into the flow, restricting tailings discharge in accordance with density changes in the pulp, and removing collected potash mineral concentrate from the surface throughout substantially the lengthwise extent of said zone.

10. A process as defined in claim 9, in which ore in a minus 6 plus 28 mesh size range constitutes the feed.

11. The process of concentrating potash minerals, which comprises the treatment of a conditioned, high-density pulp in an elongated, confined zone of substantial vertical extent, moving a high density portion of the pulp progressively along the bottom of said zone from a point of feed introduction at one end to a point of tailings discharge at its opposite end, subjecting said pulp flow to interruptions at a series of stages between feed introduction and tailings discharge in conjunction with an aerating action induced by a high-velocity discharge of an aerating composition into the lower portion of the flow, restricting tailings discharge in accordance with density changes in the pulp at the discharge end of said zone, and removing collected potash mineral concentrate from the surface throughout substantially the lengthwise extent of said zone.

12. The process of concentrating potash minerals, which comprises the treatment of a conditioned, high-density pulp' in an elongated, confined zone of substantial vertical extent, moving a high density portion of the pulp progressively along the bottom of said zone in a gravity flow from a point of feed introduction at one end to a point of tailings discharge at its oposite end, subjecting said pulp flow at a series of stages between feed introduction and tailings discharge to an aerating action induced by a high velocity discharge of an aerating composition into the lower portion of the flow, restricting tailings discharge in accordance with density changes in the pulp, and removing collected potash mineral concentrate from the surface throughout substantially the lengthwise extent of said zone.

13. The process of concentrating sylvinite ore in a coarse sized range, which comprises subjecting crushed sylvinite ore before beneficiation to a size separation for rejection of fines and coarse sizes, passing the sized ore to a desliming stage for removal of clayey constituents, conditioning the deslimed ore for flotation of less than the entire sylvite content, subjecting the ore so conditioned to a flotation separation for the recovery of a high grade, coarse sylvite concentrate, conditioning the tailings of said first flotation stage with sufi'icient collector reagent to float substantially all remaining sylvite content inclusive of middlings, subjecting theconditioned tailings to a second flotation for recovery of a middlings concentrate, subjecting the middlings concentrate to size reduction to a standard flotation size, and subjecting the reduced product to fiotationfor recovery of a standard size sylvite concentrate.

14. A process as defined in claim 13 in which the coarse reject is subjected-to size reduction with the middlings concentrate.

15. The process of concentrating the sylvite content of sylvinite ores, which comprises crushing sylvinite ore to provide a product for treatment a substantial portion of which is in sizes larger than standard flotation size, subjecting the crushed product to a size separation to reject a plus 6 mesh fraction and a second fraction on the fine size range, subjecting the remaining product to a deslim ing step, conditioning the deslimed product with a collector for sylvite in a quantity less than required to floatthe entire sylvite content, subjecting the conditioned pulp to a flotation treatment for concentration of a high grade, coarse sylvite, conditioning the tailings ofsaid first flotation with enough collector for sylvite to float substantially all the remaining sylvite content, subjecting said conditioned tailings to a flotation treatment for concentration of substantially all the remaining sylvite, reducing the second concentrate to a standard flotation size, and subjecting the standard sized product to a flotation separation for recovery of a standard sized sylvite concentrate.

16. A process as defined in claim 6, in which sylvite is collected as the froth concentrate at the final flotation stage.

17. The process of concentrating sylvinite ore ina coarse size range, which comprises subjecting crushed sylvinite ore before beneficiation to a separation for re jection of fines, coarse sizes and clayey constitutents, conditioning the ore so treated for flotation of less than the entire sylvite content, subjecting the conditioned ore to a flotation separation for the recovery of a high grade, coarse sylvite concentrate, conditioning the tailings of said first flotation stage with sufiicient collector reagent to float the entire remaining sylvite content inclusive of middlings, subjecting the conditioned tailings to a second flotation for recovery of a middlings concentrate, subjecting said middlings concentrate to size reduction to a standard flotation size, and subjecting the reduced prodnet to flotation for recovery of a standard size sylvite concentrate.

18. In a process of treating sylvinite ore, the steps of sizing crushed sylvinite ore for removal of a fine fraction, the major portion of which is in the minus 28 mesh range, desliming said sized ore, conditioning the deslimed ore with collector reagent for sylvite in a quantity less 8 than required to float the entire sylvite content of the ore, subjecting the reagentized ore to a flotation separation to obtain a high grade coarse concentrate, conditioning the non-floated material of said first flotation with additional collector reagent for sylvite in a quantity surficient to float substantially all the sylvite content, and subjecting said material to a second flotation treatment to obtain a concentrate containing substantially all the remaining sylvite content of the pulp, including middlings and subjecting the concentrate of said second flotation treatment to a further concentrating treatment to reject a portion of its sodium chloride content and to obtain an upgraded sylvite concentrate.

19. In a'process of treating sylvinite ore, the steps of sizing crushed sylvinite ore for removal of a fine fraction, the major portion of which is in the minus 28 mesh range, desliming said sized ore, conditioning the deslimed ore with collector reagent for sylvite in a quantity less than required to float the entire sylvite content of the ore, subjecting the reagentized ore to a flotation separation to obtain a high grade coarse concentrate, condi:

tioning the non-floated material of said first flotation with additional collector reagent for sylvite in a quantity sufficient to float substantially all the sylvite content, subjecting said material to a second flotation treatment to obtain a concentrate containing-substantially all the remaining sylvite content of the pulp, including middlings, reducing said second'stage concentrate to a standard flotation size, conditioning the reduced concentrate with 14 a sylvite collector reagent, and subjecting the pulp so conditioned to a froth flotation treatment.

20. Ina process of treating sylvinite ore, the steps of sizing crushed sylvinite ore for removal of a fine fraction, the major portion of which is in the minus 28 mesh range, desliming said sized ore, conditioning the deslimed ore with collector reagent for sylvite in a quantity less than required to float the entire sylvite content of the ore, subjecting the reagentized ore to a flotation 'separa tion to obtain a high grade coarse concentrate, conditioning the non-floated material of said first flotation with additional collector reagent for sylvite in a quantity suflicient to float substantially all the sylvite content, subjecting said material to a second flotation treatment to obtain a concentrate containing substantially all the remaining sylvite content of the pulp, including middlings, reducing said second stage concentrate to a standard flotation size, conditioning the reduced concentrate with a halite collector reagent, and subjecting the pulp so conditioned to a froth flotation treatment.

21. The process of concentrating potash minerals which comprises the treatment of a conditioned, high-density pulp in an elongated, confined zone of substantialvertical extent, moving a high-density portion of the pulp progressively along the bottom of said zone from a point of feed introduction at one'end to a point of tailings discharge at its opposite end with only a minor quantity of non-floated solids in suspension in the upper portion of said zone, subjecting said pulp flow at a series of stages between feed introduction and tailings discharge to an aerating action induced by a high-velocity discharge of an aerating composition into the flow, restricting tailings discharge so as to maintain a relatively high density in the tailings pulp, and removing collected potash mineralconcentrate from the surface of said elongated zone.

References Cited in the file of this patent UNITED STATES PATENTS 1,269,150

Brown Sept. 17, 1957 

1. THE PROCESS OF CONCENTRATING SYLVINITE ORE IN A COARSE SIZE RANGE, WHICH COMPRISES THE TREATMENT OF CRUSHED SYLVINITE, ORE FROM WHICH SLIMES AND FINE SIZE HAVE BEEN REMOVED, CONDITIONING SUCH ORE WITH A COLLECTOR REAGENT FOR SYLVITE, FEEDING THE ORE WITH A COLLECTOR MENT ZONE, INDUCING A PROFRESSIVE FLOW OF A HIGH DENSITY PORTION OF THE SOLIDS OF THE FEED ALONG THE LOWER PORTION OF SAID ZONE TO A POINT TAILINGS DISCHARGE FROM SAID ZONE, SUBJECTING THE ORE IN SAID FLOW TO THE ACTION OF A SUCESSION OF DOWNWARDLY SWEEPING STREAMS OF BRINE AND AIR IN THE LOWER PORTION OF SAID ZONE SO AS TO REPEATEDLY TUMBLE AND LOOSEN THE PARTICLES IN SAID PROGRESSIVE FLOW 